A model is presented for the droplet evaporation process induced by a shock wave propagating in a fog. The model is based on the existence of a quasi-steady wet bulb state of the droplets during evaporation. It is shown that for moderate shock strength, Ma = < 2, and droplet radii in the range of 1-5 gin, the major part of the evaporation process is governed by a balance between heat conduction and vapour diffusion. The formation of a fog by means of an unsteady adiabatic expansion of humid nitrogen is described. Experimental results of shock induced evaporation are shown for shock Mach numbers from 1.2 to 2.1, droplet mass fraction of 5 9 10 3, and initial droplet radii of 1-1.4 gm. The expected linear relation between droplet radius squared and time during evaporation is observed. Characteristic evaporation times appear to be strongly dependent on shock strength. A variation of about two decades, predicted by theory, was experimentally observed for the Mach number range studied.
recompressed by the reflected shock wave. Roth and Fisher (1985) report on the shock induced evaporation of submicron aerosol droplets suspended in argon with emphasis on the mass transfer behaviour of the droplets in the transition regime.
The present investigation deals with a dense cloud of small water droplets with nitrogen as a carrier gas. Typical droplet radii are in the range of 1 1.5 p.m, the droplet mass fraction being of the order of 5 9 10 3. The fog is formed by means of an unsteady rarefaction wave in humid nitrogen containing nuclei in the test section of a shock tube. Preliminary results have been reported elsewhere (Goossens et al. 1986).